Explicit modeling of pebble temperature in the porous-media model for pebble-bed reactors

In this study, a multiscale model has been developed to include an explicit pebble-temperature model nested in the porous-media model for pebble-bed reactor applications. The multiscale solid-phase energy balance model, including the pebble surface energy balance equation and an explicit modeling of pebble temperature, can predict the macroscopic (pebble bed) and microscopic (pebble) temperature distributions under both steady-state and transient conditions. The proposed multiscale model is solved in a fully coupled manner using the NewtonKrylov method, and therefore iterations between the macroscopic (pebble-bed-scale) and microscopic (pebble scale) model are avoided. Extensive code verifications, validation, and demonstrations have been performed for this newly developed model. By explicitly modeling pebble temperatures, this new model addresses a major deficiency of the basic porous-media model, which assumes homogeneous solid-phase temperature and is not appropriate for pebble-bed reactor design and safety analyses.

Automated summary

A multiscale model has been developed to include an explicit pebble-temperature model in the porous-media model for pebble-bed reactor applications. The model can predict macroscopic and microscopic temperature distributions, addressing a major deficiency of the basic model.